Due to the saturation of the mobile radio market, it frequently occurs that mobile radio users have more than one mobile telephone. For example, mobile radio subscribers often use, in addition to a first mobile telephone with a SIM (subscriber identification module) card, which is also carried, a car telephone that is formed by a second mobile telephone that can be inserted into a corresponding holding device in the vehicle or that can already be integrated in the vehicle and becomes useable by inserting a SIM card. In general, a single unambiguous telephone number is allocated to a SIM card, however, so that the corresponding mobile radio subscriber, in the case of owning a number of SIM cards, also has a number of telephone numbers which is particularly disadvantageous for the mobile radio subscriber himself and the communication partners calling him since they must know a number of mobile radio telephone numbers.
To overcome this disadvantage, it is known to assign the same telephone number to multiple mobile telephones. This service is implemented in that this one telephone number allocated to a main device is routed to the telephone numbers of the other terminals so that, in the case where this number is called, all mobile telephones of the subscriber will ring if they are registered in the telecommunication network. As soon as the subscriber accepts the call on one of the mobile telephones, the ringing of the other mobile telephones is correspondingly ended. This service is particularly comfortable and user-friendly since the mobile radio subscriber now only needs to use one mobile radio telephone number and must only inform his communication partners of this number.
With respect to sending out electronic short messages, such as SMS (short messaging service) or MMS (multimedia messaging service), this service has disadvantages, however. As soon as a number of mobile telephones can be reached via a single telephone number, an electronic short message sent to this telephone number is conveyed to all mobile telephones. Since the read state of a short message is indicated in modern mobile telephones, i.e. the corresponding short message is marked as “read” or “unread”, sending a short message to a number of mobile telephones has the consequence that the message can be marked as “read” on one of the mobile telephones and as “unread” on one or more other mobile telephones.
Furthermore, the case may occur that a mobile telephone is not registered in the network whilst another mobile telephone receives a short message and the subscriber reads the message on this device. As soon as the one mobile telephone is then registered in the network, the same short message is also supplied to it and marked as “unread” in the mobile telephone even though the message has already been read on another mobile telephone.
This leads to the mobile radio subscriber expending an increased amount of work in finding out which message is really “new” and which has already been read.